The invention relates to lubricated bearings in general, and more particularly to improvements in lubricated bearing assemblies for use in large centrifugal pumps, valves and many other types of machines. Still more particularly, the invention relates to improvements in bearing assemblies of the type wherein a substantially horizontal shaft carries and drives the rotor of a thrust bearing and the rotor is installed in a housing which receives oil or another liquid lubricant from a lubricant-containing vessel in response to rotation of the shaft.
German Pat. No. 32 03 642 discloses a bearing assembly wherein the luricant-containing vessel is a component part of a cooling unit which is mounted at a level below the rotor of the thrust bearing. A drawback of the patented assembly is that the lubricant in the vessel exchanges heat with a continuously circulated stream of a cooling medium so that the temperature of the lubricant drops below a minimum acceptable value when the machine is idle, i.e., when the lubricant does not receive heat from the rotary parts of the machine. Therefore, such bearing assemblies must be provided with heating units and with complex regulating systems which start the heating units when the temperature of the continuously cooled lubricant drops below the acceptable value. The heating units occupy substantial amounts of space and consume energy to thus increase the operating cost of the patented bearing assemblies.
German Offenlegungsschrift No. 33 19 537 discloses a lubricating system for a shaft bearing which is or is likely to be subjected to pronounced thermal stresses. The housing for the thrust bearing is mounted in and is cooled by the contents of an oil tank. That end portion of the shaft which extends into the housing carries an impeller which draws oil from the tank into the housing when the shaft is driven. The housing is spaced apart from the bottom of the tank so as to provide room for an oil sump. A drawback of this proposal is that the impeller is a separately produced part which occupies space in and thus necessitates the use of a larger housing.
A similar bearing assembly is disclosed in Brochure AT 476/82 ("Glacier Designers' Handbook No. 11") which is published by the firm Glacier, Alperton, Wembley, Middlesex, United Kingdom. A disc-shaped rotor of the thrust bearing is confined in a housing and is mounted at one end of the shaft. The housing is installed in the upper portion of an oil tank and its lower part has two openings which establish communication with the tank and enable a portion of the rotor to dip into the supply of oil so that oil is drawn into the housing and lubricates the thrust bearing when the shaft is set in motion. The peripheral surface of the rotor is surrounded by a ring which is movably mounted in the housing and whose lower portion has two axially parallel channels each of which communicates with two bores extending substantially tangentially of the rotor. One bore serves to admit oil into the respective channel and the other bore discharges oil from the channel. The oil film between the rotor and the ring turns the ring, either clockwise or counterclockwise, and the bores allow for circulation of oil through the respective channels. The ring changes its angular position in response to a change in the direction of rotation of the rotor to thus change the direction of flow of circulated oil. A drawback of this proposal is that the bearing assembly is prone to malfunction in response to penetration of contaminants and/or other foreign objects. The foreign objects can block angular movements of the ring to thus render the lubricating system imoperative.